A neurolinguistic investigation into semantic differences of evidentiality andmodality1
Yurie HARA — Hokkaido University
Naho ORITA — Waseda University
Deng YING — The University of Tokyo
Takeshi KOSHIZUKA — Tokyo University of Science
Hiromu SAKAI — Waseda University
Abstract. Corpus and EEG studies were conducted to reveal behavioral and neurological differences between processing of Japanese modals and evidentials.
Keywords: evidentiality, modality, causality, electroencephalography, Japanese.
1. Introduction
Many of the prominent studies on inferential evidentials (Izvorski, 1997; Matthewson et al.,2006; McCready and Ogata, 2007) have argued that evidentiality is a kind of modality. Davisand Hara (2014) and Hara (2017) (henceforth, D&H) argue against this evidential-as-modal
approach and make two claims: 1. The Japanese sentence-final auxiliary yooda ‘it seems’ as in(1) is a morpheme of evidentiality which is distinct from canonical modal auxiliaries like daroo‘I bet/probably’ in (2). 2. The semantics of yooda relies on the notion of causality.
(1)

Ame-ga futta yooda.
rain-NOM fell EVID
‘It seems that it rained.’(2)

Michi-ga nureteiru daroo.
streets-NOM wet
I-bet‘The streets are wet, I bet/probably.’

The goal of this paper is to justify D&H’s theoretical claims by way of corpus and EEG experiment. This paper is structured as follows: Section 2 reviews D&H’s argument and Hara’s(2017) formal analysis. In particular, yooda and daroo belong to distinct categories and thesemantics of yooda presupposes a causal relation and asserts that the speaker perceives the effect state of the causal relation. Crucially, the assertional content of yooda does not involve
semantics of modality, i.e., quantification over possible worlds. In contrast, daroo is an epistemic necessity modal and does not have a causality presupposition. Section 3 presents theresearch questions of the study. The current study investigates whether the corpus and EEG
experiment support the idea that evidentialy and modality are separate categories. Section 4
discusses the result of the corpus study, which confirms the native speaker’s intuition that p
in p-yooda expresses a cause event. Yooda tends to follow cause-denoting predicates, whiledaroo tends to follow state-denoting predicates. The corpus result alone does not reveal the
1 This project is supported by NINJAL Project “Cognitive Neuroscience of Linguistic Variation in Pragmatic In-

ference” (PI: Hiromu Sakai), JSPS Kiban (C) “Semantic-Pragmatic Interfaces at Left Periphery: a neuroscientificapproach” (18K00589; PI: Yurie Hara), and JSPS Kiban (A) “How does the grammar emerge in the human brain:
A view from comparative cognitive neurosciences of East Asian languages” (15H01881; PI: Hiromu Sakai). We
are grateful to Aine Ito, Yohei Ozeki, and Masa Yano for their help with analysis and to Tsu-Yin Chen and Saaya
Mori for their assistance in data collection.
© 2020 Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai. In: M. Franke et al. (eds.)
Proceedings of Sinn und Bedeutung 24, vol. 1, pp.273–290. Osnabrück University.

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Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai

difference between yooda and daroo with respect to whether or not the causality requirement
is semantically encoded. Section 5 presents our EEG experiment that overcomes this shortcoming of the corpus study. The felicitous yooda condition elicits LAN which is an index ofa successful causal inference (Baggio et al., 2008; Cohn and Kutas, 2015) (alternatively, theinfelicitous condition elicits N400/P600 effect). In contrast, there is no significant differencein the waveforms between the felicitous and infelicitous daroo conditions. This suggests thatyooda encodes the causality requirement in its semantics while daroo sentences give rise toa causal inference in pragmatics. Furthermore, the processing of daroo elicits N400, which isargued to be an index of an increase of cost in the processing of possible worlds (Dwivedi et al.,2006; Kulakova et al., 2014; Kulakova and Nieuwland, 2016). Section 6 concludes the paper.
2. Modality and Evidentiality
Evidentials are morphemes that signal the source of information a speaker has to make the claim(Aikhenvald, 2004; Willett, 1988). Evidential morphemes are distinguished depending on theirevidence types. For instance, Willett (1988) provides the following typology of evidence types.
Type of sources of information

Indirect

DirectAttested

ReportedInference

Visual Auditory Other Sensory Secondhand Thirdhand Folklore Results Reasoning
Figure 1: Willett’s (1988: 57) typology of evidence types
Japanese has a rich paradigm of indirect evidential markers such as yooda/mitaida/rasii ‘itseems/appears’, TP+sooda ‘I hear’, and V+sooda ‘looks like’ (Aoki, 1986; McCready andOgata, 2007; Hara, to appear). To our knowledge, the work by McCready and Ogata (2007)is the first to give a formal analysis to the Japanese indirect evidentials. According to McCready and Ogata (2007), evidential markers should be treated as a kind of epistemic modal.
Many of the leading literature on evidentiality in other languages (Izvorski, 1997; Matthewson et al., 2006) also classifies evidentiality under the general category of epistemic modality.
On the other hand, canonical modals like English must are argued to belong to the inferential
evidentials (von Fintel and Gillies, 2010; Degen et al., 2019) blurring the boundary between evidentiality and modality. By examining the semantics of Japanese inferential evidential yooda,
D&H show that evidentials constitute a category distinct from epistemic modality.

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2.1. Lack of epistemic commitment
D&H show that yooda is different from daroo in that the prejacent p in p-yooda is not an
at-issue commitment of the sentence since it is cancellable.
In (3) and (4), both a bare assertion p and p-daroo commit the speaker to p, thus p cannot becancelled.
(3)#Ame-ga futta kedo jitsu-wa futtenai.
rain-NOM fell but actually fall-NEG‘#It rained but in fact it didn’t.’(4)#Ame-ga futta daroo kedo jitsu-wa futtenai.
rain-NOM fell I-bet but actually fall-NEG‘#Probably, it rained but in fact it didn’t.’

In contrast, the prejacent p in p-yooda is cancellable as in (5).
(5)

Ame-ga futta yooda kedo, jitsu-wa futte-nai. (Dereka-ga
mizu-omaitanda.)
rain-NOM fell EVID but actually fall-NEG someone-NOM water-ACC sprayed‘It seems that it rained, but in fact it didn’t. (Someone sprayed water.)’

In short, if p-yooda were a kind of modality, it should also give rise to a (weak) commitment
to p. Since its prejacent is cancellable, yooda belongs to a different category.
2.2. Causality
D&H also claim that the notion of evidentiality needs to encode asymmetric causal dependencies: Rain causes wet streets but not vice versa. McCready and Ogata (2007) propose a
Bayesian modal semantics for a number of evidentials. In M&O’s analysis, what counts asevidence in asserting p-yooda is some information q such that learning q raised a’s subjective
probability of p. In (6), thus, a learns that the streets are wet, which has led a to raise her
subjective probability of p, hence the use of yooda is acceptable.
(6)(Looking at wet streets)
Ame-ga futta yooda.
rain-NOM fell EVID
‘It seems that it rained.’

However, D&H show that it makes wrong predictions if we switch p and q, as in (7). Learningthat it is raining should also raise the agent’s subjective probability of “the streets are wet”, thus
M&O wrongly predict that yooda would be acceptable in (7).
(7)

(Looking at falling raindrops)#Michi-ga nureteiru yooda.
streets-NOM wet
EVID‘#It seems that the streets are wet.’

From this observation, D&H propose that what counts as evidence in asserting p-yooda is some
information q such that p causes q.

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Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai

Daroo seems to be in a complementary distribution with yooda. That is, p-daroo is infelicitouswhen the speaker learns information q such that p causes q as in (8), while it is felicitous when
the information q is such that q causes p as in (9).
(8)(Looking at wet streets)#Ame-ga futta daroo.
rain-NOM fell I-bet‘#Probably, it rained.’(9)(Looking at falling raindrops)
Michi-ga nureteiru daroo.
streets-NOM wet
I-bet‘Probably, the streets are wet.’

We assume with Hara and Davis (2013) that unlike the case of yooda, the causality is notlexically encoded in the semantics of daroo. Rather, the above contrast is a result of pragmaticcompetition. Yooda has a stronger semantics since it requires a more specific context thanyooda. Since yooda is a better candidate fo the context in (8), daroo is infelicitous in (8). See
Hara and Davis (2013) for details.
To conclude, the semantics of p-yooda is dependent on causality. More specifically, p in pyooda denotes a cause event in a causal relation, p causes q. In contrast, the seeming causal
requirement on the use of daroo arises as a result of pragmatic competition.
2.3. Semantics of daroo and yooda
Given D&H’s observation, Hara (2017) formulates the semantics of yooda in Kaufmann’s(2013) Causal Premise Semantics, which incorporates causal networks to Kratzer’s (2005)
premise semantics. Let f and g be premise background and ordering source respectively andw a possible world. Premise structure Prem((f∗ g)(w)) is obtained by ranking Kratzer premisesets.2 Basic modal operators, Must and May, are defined as follows:
(10)

a.
b.

Must(p) is true at f, g, w iff p is a necessity relative to Prem((f∗ g)(w)).
May(p) is true at f, g, w iff p is a possibility relative to Prem((f∗ g)(w)).

We propose that daroo is a necessity modal, with the following interpretation:3(11)

Interpretation of daroo: Daroo(p) is true at f, g, w iff Must(p) is true at f, g, w.

Turning to the evidential yooda, Hara’s (2017) formalization of causality is built on the interpretation of conditionals. In the current framework, we obtain a causal premise background fc [p]by hypothetically updating a causal premise background fc with the antecedent proposition p
as in (12).
(12)

Hypothetical update: For all w: f[p](w) := {{p}}∗ f(w).

Thus, ‘p causes q’ is formulated as Must p (q) in (13):2 Many of the definitions are omitted for space reasons. See Hara (2017) and Kaufmann (2013).
3 Daroo has some other interesting lexical restrictions which are irrelevant to the current purpose of the study. See

Hara (2006, 2018).

A neurolinguistic investigation into semantic differences of evidentiality and modality
(13)

277

Causal rule: Must p (q) is true at fc , g, w iff Must(q) is true at fc [p], g, w.

Finally, we define the interpretation of yooda. As shown by D&H, asserting p-yooda does notcommit the speaker to p, thus p contributes to the antecedent part of the conditional rather
than the consequent, i.e., Must p (q). In Hara’s (2017) original definition, the causal component
Must p (q) was part of the asserted content. Here, we differ from Hara’s (2017) original analysis
and place the causal component in the presupposition since it is part of the common groundand it is not asserted (e.g., in uttering (1), the speaker is not asserting ‘rain causes wet streets’
but assuming that it is commonly known.). Thus, the interpretation of yooda is defined as in(14): Yooda(p) presupposes that there is some state q such that q is a necessity relative toPrem((fc [p]∗ g)(w)) and asserts that the speaker perceives q at w.
(14)

Interpretation of yooda:
Yooda(p) is defined at fc , g, w iff ∃q such that Must p (q) is true at fc , g, w.
(presupposition)
If defined, Yooda(p) is true at w iff the speaker perceives q at w.
(assertion)

As can be seen in (14), the assertion of p-yooda is evaluated only at the single actual/utterance
world w. As with D&H, our definition (14) correctly derives the interpretations and distributions of yooda discussed above. In (5), the speaker presupposes that raining causes wet streetsand she only asserts that she observed wet streets, which are usually caused by raining but
could be caused by other factors, e.g., someone sprayed water with a hose. (7) causes a presupposition failure since we know, as background knowledge, that wet streets do not causerain.
In summary, yooda belongs to the category of evidentiality which is distinguished from that ofmodality such as daroo. The semantics of p-yooda includes a presupposition that there is an
event q such that p causes q. The assertion of p-yooda does not commit the speaker to p but
only entails that the speaker perceives q. In contrast, p-daroo is an epistemic necessity modal,
the semantics of which involves quantification over possible worlds, thus the assertion of it
commits the speaker to p. Furthermore, daroo does not have a causality presupposition likeyooda. As discussed in Section 2.2, the apparent causal restriction that p in p-daroo needs todenote an effect state is a result of pragmatic competition.
3. Research Questions
The previous section summarized D&H’s claims that evidentials and modals are separate categories and that the interpretation of yooda is dependent on causality. The goal of this paper is
to empirically justify these claims using corpus and an EEG experiment:(15)

Research Question 1
Can we justify the theoretical claims by way of corpus/EEG studies?

(16)

Research Question 2
Are there neural indices that indicate the computational difference between modals
and evidentials?

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Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai
Table 1: NPMI
yooda
past
0.22
>
non-past
0.177 <
verb
0.204 >
verb-positive 0.196 >verb-negative 0.209 <adjective
0.116 <

daroo
0.057
0.214
0.188
0.17
0.253
0.135

4. Corpus
We conducted a corpus study to test whether the distribution of yooda is dependent on thecausal relation. Since the corpus does not contain information on whether a predicate denotes
a cause or effect, we made the assumptions in (17) and the predictions in (18):
(17)

a.
b.

Causes are events while effects are states.
The cause event temporally precedes the effect state.

(18)

a.
b.

Yooda tends to be attached to past-tensed and eventive predicates.
Daroo tends to be attached to non-past and stative predicates.

To test the predictions in (18), we use Balanced Corpus of Contemporary Written Japanese(BCCWJ) (Maekawa et al., 2014) containing approximately 100 million words collected fromvarious kinds of Japanese texts. We extract sentences ending with daroo and yooda, resulting
in 30686 yooda sentences and 47538 daroo sentences. We measured Normalized Pointwise
Mutual Information (NPMI): The higher positive values of NPMI indicate stronger associations
or positive correlations between kinds of predicates and final auxiliaries yooda/daroo.4 Table 1
summarizes the result. As predicted, yooda has better associations with past-tensed predicatesand positive verbs, which tend to denote events, while daroo has better associations with nonpast predicates and negative verbs and adjectives, which tend to denote states (Krifka, 1990).
In short, yooda is more likely to follow past-tensed predicates and positive verbs, which are
likely to denote cause events, than non-past predicates and negative verbs and adjectives, which
are likely to denote effect states. This result is in accordance with D&H’s claim that causality
is crucial in the interpretation of yooda: p in p-yooda denotes a cause event in a causal relation.
The current result also shows that daroo is more likely to follow non-past predicates, negative
verbs and adjectives, which are likely to denote effect states. As discussed in Sections 2.2 and
2.3, the lexical semantics of daroo does not involve causality requirement. Thus, we interpret
this result as an outcome of the pragmatic competition between yooda and daroo.
5. EEGAn EEG experiment was conducted to address the research questions laid out above in Section
3.
4 NPMI is represented by a value between [−1, +1]. If two predicates have zero co-occurrence, NPMI is −1. Ifthey are independent, it is 0. If they always co-occur, it is +1. See Bouma (2009).

A neurolinguistic investigation into semantic differences of evidentiality and modality279

5.1. Participants
Thirty-eight right-handed native Japanese speakers were paid to participate in this study. Six
participants were excluded from the analysis because of facility disorder. After artifact rejection, two more participants were excluded from the analysis due to the extremely small numberof valid trials in their data (less than 15 trials in at least one of the conditions). The final analysis was conducted with 30 participants (16 males, mean age 20.9 years, age range 18 to 24
years). All participants were right-handed and reported normal vision without any history ofneurological or psychiatric disorders. Written consent was obtained from all participants.
5.2. Stimuli
The stimuli had two fully-crossed factors—CONTEXT (Effect-Cause/Cause-Effect) and SFA(sentence-final-auxiliary; yooda/daroo)—which resulted in four conditions:
(19)

a.

b.

c.

d.

ECy: Effect-Cause-yooda :Michi-ga nureteiru. Ame-ga futta yooda.
streets-NOM wet
rain-NOM fell EVID‘The streets arer wet. It seems that it rained.’
CEy: Cause-Effect-yooda:#Ame-ga futta. Michi-ga nureteiru yooda.
rain-NOM fell streets-NOM wet
EVID‘#It rained. It seems that the streets are wet.’
CEd: Cause-Effect-daroo:
Ame-ga futta. Michi-ga nureteiru daroo.
rain-NOM fell streets-NOM wet
I-bet‘It rained. The streets are wet, probably.’
ECd: Effect-Cause-daroo:#Michi-ga nureteiru. Ame-ga futta daroo.
streets-NOM wet
rain-NOM fell I-bet‘The streets are wet. It rained, probably’

ECy is a fit condition where the final auxiliary yooda, which semantically presupposes that
there is a causal relation and attaches to a proposition that denotes the cause event, matches
the Effect-Cause context. CEy is an anomalous condition where yooda is attached to the effectstate in a causal relation. CEd is a fit condition where the final auxiliary daroo is attached toa conclusion drawn from premises. ECd is an anomalous condition, but unlike CEy, which issemantically anomalous, it is pragmatically anomalous. That is, as argued in Section 2, unlike
yooda, daroo does not lexically encode a causal relation in its semantics. (19d) is anomalous
because yooda, which semantically encodes the causal requirement, is more optimal in the
Effect-Cause context.
All the stimuli were normed for naturalness by Japanese native speakers.
5.3. Procedure
Each condition had 78 items. 78 fillers were included. The experiment was counterbalanced
so that one participant will not see the same context twice (234 trials in each experiment). The

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Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai

procedure of a trial is depicted in Figure 2. Each trial started with a fixation cross shown for
600ms. After 300ms blank screen, each word of the first sentence was presented for 600ms withan inter-word interval of 300ms. After the first sentence was presented, a ‘˜’ sign is presented
for 600ms to let the participants to blink. After 300ms blank screen, the second sentence waspresented. At the end of each filler trial, subjects were asked to give a yes/no response to an
acceptability judgement task.

Figure 2: Procedure of a trial
5.4. Recording
EEG was recorded using AC amplifiers (Brain Products) from 32 electrodes equipped in anelastic cap (EASYCAP) according to the International 1020 system. Electrodes included thefollowing positions: FP1, FP2, F7, F3, Fz, F4, F8, FC5, FC1, FC2, FC6, T7, C3, C1, Cz, C4,
T8, CP5, CP1, CP2, CP6, TP9, P3, Pz, P4, P8, TP10, O1, and O2. Another electrode was placedat nose for online referencing. Offline, all electrode sites were re-referenced to the average ofthe right and left mastoids. The electro-oculogram (EOG) was located at the outer canthus ofright eye in order to detect horizontal eye movements and blinks. Scalp impedances were kept
below 5 kΩ. The continuous EEG was digitized at 250 Hz and filtered offline (high-pass at 0.5
Hz and low-pass at 40 Hz).
5.5. Analysis
ERPs were calculated by averaging the EEG time-locked to a point 200ms pre-stimulus onset
and lasting until 1000ms after the onset of the stimulus. The 200ms pre-stimulus period wasused as a baseline. Trials containing ocular or muscular artifacts, were not taken into consideration in the averaging process. Based on visual inspection of ERP waveforms and the time
windows of potential effects, two time windows were selected for statistical analyses: 300-

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281

500ms and 500-700ms. Repeated-measures ANOVA (anovakun 4.8.35 implemented in R (RCore Team, 2019)) were performed with the factors CONTEXT (Cause-Effect/Effect-Cause),
SFA (sentence-final auxiliary; yooda/daroo) and ROI (regions of interests). Six ROI s are obtained by calculating the mean of the three electrodes in each region (anterior-left (AL; F3 ,F7,
FC5); anterior-right (AR; F4, F8, FC6); central-left (CL; FC1,CP1,CP5); central-right (CR;
FC2,CP2,CP6); posterior-left (PL; P3, P7, O1); posterior-right (PR; P4, P8, O2)) as in Figure
3.

Figure 3: 6ROI (Taken from Kulakova et al. (2014))
5.6. Result
A 2 × 2 × 6 repeated measures ANOVA with the factors CONTEXT (CE/EC), SFA (y/d) and ROI
in the 500-700ms time window revealed a three-way interaction (F(5, 145) = 3.19, p < .01;
Figure 4). The ECy condition elicited a significantly more negative-deflection at AL comparedto CEy (F(1, 29) = 8.06, p < .01). At PR, the CEy condition elicited a significantly morenegative-deflection at (F(1, 29) = 7.03, p < .05) compared to ECy. In EC conditions, yooda
was significantly more negative compared to daroo in AL (F(1, 29) = 18.63, p < .001), PL(F(1, 29) = 5.63, p < .05) and PR (F(1, 29) = 17.51, p < .001). There was no significant
difference between ECd and CEd conditions nor between CEy and CEd. Detailed test-statistics
in the 500-700ms time window are shown in Table 2.
5 http://riseki.php.xdomain.jp/

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Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai(a) Grand average waveforms time-locked to the final auxiliary(b) Conditions(c) ECy−CEy

Figure 4: 3-way interaction

A neurolinguistic investigation into semantic differences of evidentiality and modality

SFA
CONTEXTROISFA × CONTEXTSFA × ROICONTEXT × ROISFA × CONTEXT × ROI

df
1,29
1,29
5,145
1,29
5,145
5,145
5,145

F
3.78
0.98
7.11
0.07
4.95
1.68
3.19

p
0.06
0.32
< 0.001
0.786< 0.0010.1409
0.009

sig.
+
ns
***
ns
***
ns
**

5,145
1,29
1,29
1,29
1,29
1,29
1,29

4.09
9.57
2.08
0.35
0.09
2.95
6.88

0.0017
0.004
0.15
0.55
0.75
0.09
0.01

**
**
ns
ns
ns
+
*

5,145

0.18

0.96

ns

5,145
1,29
1,29
1,29
1,29
1,29
1,29

7.2692
18.63
1.13
0.14
0.57
5.63
17.51

< 0.001< 0.001
0.29
0.70
0.45
0.02
< 0.001

***
***
ns
ns
ns
*
***

5, 145

0.40

0.84

ns

283

SFA (yooda)
CONTEXT × ROICONTEXT at AL
CONTEXT at AR
CONTEXT at CL
CONTEXT at CR
CONTEXT at PL
CONTEXT at PR
SFA (daroo)
CONTEXT × ROICONTEXT (EC)SFA × ROISFA at AL
SFA at AR
SFA at CL
SFA at CR
SFA at PL
SFA at PR
CONTEXT (CE)SFA × ROI

Table 2: Test-statistics of the ERPs in the 500-700ms time window
A 2 × 6 repeated measures ANOVA with the factors SFA and ROI in the 300-500ms time window revealed that there was a significant SFA × ROI interaction (F(5, 145) = 7.12, p < .001;
Figure 5). Daroo elicited a significantly more positive-deflection at AL (F(1, 29) = 12.44, p <.01) and a significantly more negative-deflection at central (CL: F(1, 29) = 5.30, p < .05;
CR: F(1, 29) = 12.97, p < .01) and posterior (PL: F(1, 29) = 4.85, p < .05; PR: F(1, 29) =12.14, p < .01) regions compared to yooda. There was also a significant CONTEXT × ROI interaction (F(5, 145) = 3.00, p < .05). The CE conditions were significantly more negative compared to the EC conditions at PL (F(1, 29) = 4.44, p < .05) and PR (F(1, 29) = 6.05, p < .05).
Detailed test-statistics in the 300-500ms time window are shown in Table 3.

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Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai(a) Grand average waveforms time-locked to the final auxiliary(b) Conditions(c) daroo−yooda

Figure 5: SFA × ROI interaction

A neurolinguistic investigation into semantic differences of evidentiality and modality

SFA
CONTEXTROISFA × CONTEXTSFA × ROICONTEXT × ROISFA × CONTEXT × ROI

df
F
p
1,29
14.99 < 0.001
1,29
2.78
0.10
5,145 5.11
< 0.001
1,29
0.006 0.93
5,145 7.12
< 0.001
5,145 3.00
0.01
5,145 1.63
0.15

sig.
***
ns
***
ns
***
*
ns

1,29
1,29
1,29
1,29
1,29
1,29

12.44
0.58
5.30
12.97
4.85
12.14

0.001
0.45
0.02
0.001
0.03
0.001

**
ns
*
**
*
**

1,29
1,29
1,29
1,29
1,29
1,29

0.79
1.74
0.15
0.006
4.44
6.05

0.37
0.19
0.69
0.93
0.04
0.02

ns
ns
ns
ns
*
*

285

SFA × ROISFA at AL
SFA at AR
SFA at CL
SFA at CR
SFA at PL
SFA at PR
CONTEXT × ROICONTEXT at AL
CONTEXT at AR
CONTEXT at CL
CONTEXT at CR
CONTEXT at PL
CONTEXT at PR

Table 3: Test-statistics of the ERPs in the 300-500ms time window
5.7. Discussion
5.7.1. Semantics/Pragmatics of Causality
We interpret the anterior negativity elicited by the ECy condition (Figure 6) as Left-Anterior
Negativity (LAN), which is argued to be a correlate of successful causal inference (Baggio
et al., 2008; Cohn and Kutas, 2015).

Figure 6: LAN (elicited by ECy) or P600 (elicited by CEy)

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Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai

An alternative interpretation is to regard an anterior negativity elicited by the ECy condition(Figure 6) as a positivity elicited by the CEy condition. In this interpretation, the negativity
observed in Figure 7 and the positivity observed in Figure 6 are N400/P600 pattern causedby semantic anomaly and reanalysis. Frontal P600 may seem unconventional because P600
elicited by grammatically anomalous constructions is usually observed in posterior regions(e.g., Coulson et al., 1998). However, Kaan and Swaab (2003) report that frontal P600 is anindex of ambiguity resolution and processing difficulty in discourse. Indeed, Dwivedi et al.
(2006) observe left-frontal P600 for anomalous discourse. Furthermore, when the experiment
involves an acceptability judgment task, it is reported that semantically anomalous constructions tend to yield N400 followed by P600 (Kuperberg, 2007; Kulakova et al., 2014), althoughin Kuperberg (2007); Kulakova et al. (2014), P600 is found in central/posterior regions.

Figure 7: N400 (elicted by CEy)
Between the two interpretations, we find the first more tenable than the latter. If the ECy
condition elicits LAN, only ECy is predicted to deflect negative compared to the other three
conditions. Similarly, if CEy elicits P600, only CEy is predicted to deflect positive compared tothe other three. In the current experiment, there was a significant difference not only between
ECy and CEy but also between ECy and ECd. That is, ECy was more negative compared toboth CEy and ECd at AL. In contrast, there was no significant difference between CEy andCEd. Thus, we regard the negativity elicited by ECy is LAN, which indexes successful causal
inference.
While significant differences between the two yooda conditions were obtained, there was no
significant difference between the two daroo conditions, CEd and ECd. We attribute this difference between two auxiliaries to the status of causality in each morpheme. That is, as argued
in Section 2, the ECd is only pragmatically anomalous since there is a better auxiliary, namely
yooda, which fits the Effect-Cause context. Thus, pragmatic anomaly is not strong enough toaffect the waveforms. In contrast, CEy is semantically anomalous since the semantics of yooda
requires the morpheme to be attached to the cause event of a cause-effect relation.

A neurolinguistic investigation into semantic differences of evidentiality and modality287

5.7.2. Modality and N400
We regard the posterior and central negativity observed as SFA × ROI interaction for daroo(Figure 8) as N400. Let us consider the frequencies of the two morphemes, yooda and daroo,
because we compare them directly and the amplitude of the N400 is known to be affected by
the frequency of words (Van Petten and Kutas, 1990). That is, infrequent morphemes elicit
amplified N400 compared to high frequent ones. As seen in Section 4, however, daroo is more
frequent than yooda in BCCWJ (30686 yooda sentences and 47538 daroo sentences). Since
daroo, which is more frequent than yooda amplifies N400, the observed N400 cannot be explained in terms of the frequencies of the morphemes. Instead, we propose that the observed
N400 is related to the processing of modality which involves processing of multiple possible
worlds that poses increased processing demands. This accords well with the findings in theprevious studies: Processing of English and German counterfactuals and modals elicit negativity, which is analyzed as an indication of increased processing costs. Dwivedi et al. (2006)
report that hypothetical contexts in English elicit negative trend. Kulakova et al. (2014) observethat German subjunctives elicit LAN compared to indicatives. Kulakova and Nieuwland (2016)
show that English counterfactuals elicit larger N400 compared to indicatives. We do not havemuch to say about the frontal positivity (FC5 in Figure 8(c)). Since this positivity is observed in
the same time-window as the posterior negativity is observed, it might also reflect the semantic
processing of modality.
An alternative interpretation to the semantic N400 is to interpret it as a result of lexical integration cost. The negativity for daroo condition can also be regarded as the positivity for the yooda
condition. Since yooda is more frequently used in the Effect-Cause context as we pointed out
in Section 4, its semantic integration might be less costly, which leads to less negativity of theyooda condition. This interpretation, however, does not explain why yooda in Cause-Effectcondition elicits more negativity and cancels out the reduction of negativity in Effect-Cause
context. We thus regard the semantic N400 interpretation as more favorable.

(a) Pz(b) Cz(c) FC5

Figure 8: N400 elicited by daroo

5.7.3. Summary
We observe that the evidential auxiliary yooda which marks an inference from an effect state
to a cause event elicited LAN. The alternative interpretation of the result is that the anomalous288

Yurie Hara, Naho Orita, Deng Ying, Takeshi Koshizuka and Hiromu Sakai

CEy condition elicits N400/P600 effect of semantic anomaly and reanalysis. On the other hand,
the modal auxiliary daroo elicits neither effects, even though introspection-based data suggeststhat ECd is anomalous. Our result demonstrates that causal inference involved in daroo isdifferent from that of yooda. More specifically, ECd is pragmatically anomalous while CEyis semantically anomalous. Furthermore, our result reveals that processing of modality, which
involves processing of multiple possible worlds, induces N400 effect.
6. Conclusion
Evidentiality and modality are very similar notions and often one is subsumed under the other.
Davis and Hara (2014), however, argue that evidentiality and modality are separate categories
and Hara (2017) offers a formal analysis of the Japanese evidential auxiliary yooda that lexically encodes the causal requirement in its semantics. Yooda is an evidential morpheme andp-yooda presupposes that there is information q such that p causes q and asserts that the speaker
perceives q at the actual world w@ . Hence, there is no quantification over possible worlds involved in the assertional content of p-yooda. In contrast, daroo is an epistemic necessity modal
which involves universal quantification over possible worlds and its semantics does not encode
the causal requirement. To conclude the paper, let us go back to our research questions:(15)

Research Question 1
Can we justify the theoretical claims by way of corpus/EEG studies?

(16)

Research Question 2
Are there neural indices that indicate the computational difference between modals
and evidentials?

First, the corpus and EEG studies support the idea that the interpretation of yooda is dependent
on causality and evidentials and modals are separate categories. In the corpus study, yooda
is more likely to follow cause-denoting predicates than state-denoting predicates. The corpus
result also suggests that the interpretation of daroo is also dependent on causality since daroo
is more likely to follow state-denoting predicates than cause-denoting predicates. However, theEEG study shows that the effect of causality is stronger in yooda than daroo. The ECy condition where the causal context matches the semantics of yooda elicits LAN (alternatively theanomalous CE condition elicits N400/P600 effect), while no effect is observed for the CEd and
ECd conditions. This result is in accordance with our theoretical claim that yooda semanticallypresupposes a causal relation while daroo lacks such a presupposition. The seeming influenceof causality in the introspection-based and corpus data is due to a pragmatic competition.
Regarding Research Question 2, we find LAN as an index of successful causal inference inevidentiality and N400 as an index of an increase of processing cost of modality, i.e., multiple
possible worlds.
Finally, the study reported in this paper demonstrates that EEG plays a crucial role in dissociating semantic violations from pragmatic ones. Both the introspection-based approach and the
corpus study show that the interpretation/distribution of daroo is dependent on causality justlike yooda, but neither can distinguish the nature of the violations.
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